Problem Details:

Email works via outlook web access at home but not regular Outlook
Outlook connects fine at work and experiences no problem

Solution:

Edit the exchange proxy settings to allow the user to connect to the exchange server from home

Outlook 2007

Go to Tools > Account Settings
Click Change
Click More Settings
Click on the Connection tab
Click the check box next to Connect to Microsoft Exchange Using HTTP
Click the Exchange Proxy Settings button
Underneath Connection Settings in the text field below "Use this URL to connect to my proxy server for Exchange" type in the name of the exchange server that is being used